Somewhere in the world, right now, an airliner full of people is being hit by roughly 200,000 amps of electricity. Most of them will land on time and never mention it. The cabin crew will finish the service. Some passengers will have seen a white flash and heard a bang like a door slamming; plenty will have noticed nothing at all.
Every commercial aircraft flying today is struck by lightning about once a year, or roughly once every 1,000 flight hours. No airliner has been lost to a lightning strike in more than five decades. Here is why that is true, what the bolt actually does to the aeroplane, and the separate question of whether it is safe to fly near a thunderstorm at all, which has a much more interesting answer.
The aircraft usually causes the strike itself
This is the fact that surprises people most: around 90 percent of strikes are triggered by the aircraft, not received from a storm that was going to discharge anyway. An aluminium tube moving at hundreds of miles an hour through a charged region of cloud distorts the electric field around it enough to start the discharge. The aeroplane is not a bystander that got unlucky. It is the trigger.
That also explains where and when strikes happen. They cluster between about 5,000 and 15,000 feet, during climb and descent, in the temperature band around freezing where charge separation in cloud is strongest. They are seasonal too: something like 60 percent occur between March and July in the northern hemisphere.
What the bolt actually does
The lightning does not pass through the cabin. It passes around it.
An airliner is a Faraday cage: a conductive shell that carries charge across its outside surface and leaves the interior alone. The bolt attaches at an extremity, usually the nose, a wingtip or the leading edge of a wing, and current flows along the skin. As the aircraft keeps flying, the attachment point sweeps backwards along the fuselage until the current exits at another extremity, typically the tail. Manufacturers map the airframe into strike zones and design each zone for the current it will have to carry.
On the trailing edges you will see small pointed rods, a few inches long. Those are static wicks, and they bleed accumulated static charge back into the air, which both helps the exit and stops the build-up from wrecking radio reception.
Everything vulnerable is protected on the assumption that this will happen repeatedly over the aircraft’s life: fuel tanks are designed so no spark can reach vapour, fuel lines are bonded, and avionics are shielded and surge-protected. Certification requires the aircraft to survive it and keep flying.
Carbon fibre made this harder, not easier
Aluminium conducts beautifully. Carbon fibre composite does not, at least not well enough, which became a real engineering problem when aircraft like the 787 moved to a predominantly composite fuselage.
The solution was to put the metal back in, invisibly. Composite skins are built with a conductive layer worked into the surface: expanded copper foil or an interwoven wire fabric laid into the outer plies, bonded through to structural frames so the current still has a continuous path from nose to tail. Leading edges, sensors and antennas get dedicated strike pads and diverters. It works, which is the important part, but it is an added layer of design rather than a free property of the material.
The accident that changed everything
The reason all of this exists is Pan Am Flight 214, on 8 December 1963. The Boeing 707 was holding near Elkton, Maryland, on approach to Philadelphia when lightning struck. The bolt ignited fuel vapour in a wing tank, the left wing came apart, and all 81 people on board were killed.
That crash drove the fuel-system protections, the bonding requirements and the discharge design that every airliner has carried since. It remains the last fatal airline accident caused by a lightning strike, more than sixty years ago. Aviation safety is largely a list of things that were fixed the hard way, and this is one of the clearest examples on that list.
So what does a strike cost?
Not nothing. A strike triggers a mandatory inspection before the aircraft flies again, and engineers go looking for the entry and exit points: small burn marks, pitting, a scorched rivet, occasionally a neat hole through a wingtip or a damaged static wick or antenna. Most of the time the damage is cosmetic and the aircraft is released. Sometimes a panel has to be replaced.
The real cost is time. An aircraft sitting on a stand waiting for an inspection is an aircraft not flying a schedule, and across the industry lightning is estimated to cost airlines over $2 billion a year once delays and cancellations are counted. The bolt is survivable. The downtime is expensive.
The better question: is it safe to fly near a thunderstorm?
Here is the thing pilots would want you to understand. Lightning is the part passengers worry about, and it is the part the aircraft is engineered to shrug off. The reasons crews take thunderstorms seriously are the other hazards, and they extend far outside the cloud you can see.
- Hail. A strong updraft can throw hailstones out of the top of a storm and sideways into apparently clear air, a long way downwind. Hail is what smashes windscreens and dents leading edges.
- Turbulence. Severe turbulence lives in and around the storm, including in clear air near it.
- Wind shear and microbursts. A column of descending air hitting the ground and spreading outwards can rob an aircraft of lift at exactly the point in the approach where there is no height to trade. This is the genuinely dangerous one, and it is why airports have ground-based shear detection and aircraft have predictive windshear systems.
That is why the working rule is to give significant cells a wide berth, commonly 20 nautical miles, rather than threading between them. And crucially, the onboard weather radar shows precipitation, not turbulence, not dry microbursts and not the electrical field. A gap on the radar screen is not a guarantee of a smooth gap in the sky, so the margin does work the radar cannot.
Which is the honest answer to “is it safe to fly in a thunderstorm”: airliners do not fly through thunderstorms. They fly around them, sometimes by a long way, and the diversion you resent is the safety system working. Flying in rain, by contrast, is entirely routine.
If you like knowing what the aircraft is quietly built to survive, our piece on what happens when a bird hits a plane covers the tests engines have to pass, and what a black box actually records covers what survives when things do go wrong.
Frequently asked questions
Can a plane get struck by lightning?
Yes, and it happens constantly. Every commercial aircraft is struck roughly once a year, or about once per 1,000 flight hours. Around 90 percent of those strikes are triggered by the aircraft itself passing through a charged region of cloud.
What happens if a plane gets struck by lightning?
The current travels across the outside of the airframe, entering at an extremity such as the nose or a wingtip and exiting at another, usually the tail. The cabin, fuel and avionics are protected. Passengers may see a flash and hear a bang; the flight normally continues.
Has a plane ever crashed because of lightning?
Pan Am Flight 214 in December 1963, when lightning ignited fuel vapour in a wing tank, killing 81 people. It remains the last fatal airline accident attributed to a lightning strike, and it drove the protections used ever since.
Is it safe to fly in a thunderstorm?
Airliners avoid thunderstorms rather than fly through them, typically keeping 20 nautical miles from significant cells. The danger is hail, severe turbulence and wind shear, which reach well beyond the visible cloud, rather than the lightning itself.
Is it safe to fly in the rain?
Yes. Rain on its own is routine and aircraft are designed and certified to operate in it. What crews avoid is the convective weather that sometimes comes with it.
What are the little spikes on the back of the wings?
Static wicks, or static dischargers. They bleed built-up static charge off the airframe into the air, which protects radio and navigation reception and helps current leave the aircraft.
Sources: FAA guidance on thunderstorm avoidance; Flight Safety Foundation; Mainblades lightning-strike statistics; CompositesWorld on composite lightning-strike protection; NTSB findings on Pan Am Flight 214.
